25 C. Postal stamp "Merkur head" with overprint in type I, common, horizontal over all fours stamps walking overprint, variety "inverted overprint" properly franked more franking on cover from "Ghyvelde 29.07.1940" to Dunkerque with reverse arrival postmark from "30.07.1940", faultless condition, left upper stamps minimal shaded perf tip (insignificant), expertise Lothar Herbst VP (2018) : "the other condition is perfect. The stamps are only in very small number of pieces known, therefore are they very rare. ", Michel 1.500.-